great choice David, my nearly six year old son loves his islabike.
Make sure you measure up for the small or the large, as there are two sizes of beinn 20. If you're buying for a six year old, you'll probably want the large.
If that doesn't work out the other bike I recommended to a friend who has a nearly six year old is the Cube Kid 200, http://www.cyclesurgery.com/pws/UniqueProductKey.ice?ProductID=CCUB0129WB which has no heavy suspension fork, but it is a bit more of a mountain bike than a hybrid / 'cross frame.